Add blinky logic and pw_string

Change-Id: Ia762593a241d14b796250f36ae0f4f50a214617b
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/quickstart/zephyr/+/201812
Reviewed-by: Yuval Peress <peress@google.com>
3 files changed